When I grow up people left was considered a strange society, especially in the past. People, it's a chance to marry left less than an opportunity to produce, so the people left, so there is less genetic-based.
When growing up left-handed was seen as a strange society, particularly in the past. Left-handed people are less likely to marry, so that left-handed people the opportunity to produce, so there is less hereditary.
When I grow up left-handed were considered strange, especially in the past. A left-handed person have married less than, so production opportunities the left-handed by heredity is less.